Reduced friction lift pin

ABSTRACT

A substrate support is provided that features a lift pin having at least one larger diameter shoulder section that forms a relief region between the lift pin and a guide hole disposed through a substrate support. The shoulder section minimizes contact between the substrate support and lift pin guide hole, thereby reducing pin scratching, particle generation, component wear, and increasing the useful life of the pin. In another embodiment, a flat-bottom tip is provided to promote self-standing of the lift pin, reducing pin tilting or leaning of the lift pin within the guide hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/241,005, filed Sep. 10, 2002, which issued May 3, 2005 as U.S. Pat.No. 6,887,317.

FIELD OF THE INVENTION

The present invention relates generally to an apparatus forsemiconductor processing. More specifically, the invention relates to alift pin utilized for spacing substrates from a substrate support.

BACKGROUND OF THE INVENTION

Integrated circuits have evolved into complex devices that includemillions of transistors, capacitors and resistors on a single chip. Theevolution of chip design results in faster circuitry and greater circuitdensity. As the demand for integrated circuits continues to rise, chipmanufactures have demanded semiconductor process tooling havingincreased wafer throughput, greater product yield, and more robustprocessing equipment. To meet demands, tooling is being developed tominimize particle contamination and increase the service life of toolcomponents.

One source of particle generation is the lift pins utilized to space asubstrate from a substrate support, typically in a processing chamber.The lift pins generally reside in guide holes disposed through thesubstrate support. The upper ends of the lift pins are typically flaredto prevent the pins from passing through the guide holes. The lower endsof the lift pins extend below the substrate support and are actuated bya lift plate that contacts the pins at their lower ends. The lift plateis movable in a vertical direction between upper and lower positions. Inthe upper position, the lift plate moves the lift pins through the guideholes formed through the substrate support to extend the flared ends ofthe lift pins above the substrate support, thereby lifting the substrateinto a spaced apart relation relative to the substrate support tofacilitate substrate transfer.

One problem that has been observed in the prior art is particlegeneration attributed to contact between the lift pins and the guideholes as the lift pins move through the substrate support. Specifically,contact of the sides of the lift pin with the bottom edge of the guidehole may cause deep scratches over the entire length of the lift pin.Additionally, as the scratched pin repeatedly passes through the guideholes of the substrate support, the lift pin becomes more susceptible tobinding and galling, resulting in shortened lift pin service life.

Therefore, there is a need in the art for an improved lift pin.

SUMMARY OF THE INVENTION

An improved lift pin design for spacing a substrate from a substratesupport is provided. The lift pin features at least one larger diametershoulder section that forms a relief region between the pin and a guidehole disposed through a substrate support. The shoulder sectionminimizes contact between the substrate support and lift pin guide hole,thereby reducing pin scratching, particle generation, component wear,and increasing the useful life of the pin. In another embodiment, aflat-bottom tip is provided to promote self-standing of the lift pin,reducing pin tilting or leaning of the lift pin within the guide hole.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the invention can be readily understood by consideringthe following detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a sectional view of a metal deposition chamber;

FIG. 2 is a sectional view of a lift pin assembly; and

FIGS. 3-6 depict elevations of various alternative embodiments of a liftpin according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally provides an apparatus for processing asemiconductor substrate. The invention is illustratively utilized in aprocessing system, such as a Txz® CVD processing system, available fromApplied Materials, Inc., of Santa Clara, Calif. However, it should beunderstood that the invention may be incorporated into other chamberconfigurations such as physical vapor deposition chambers, etchchambers, ion implant chambers, and other semiconductor processingchambers.

FIG. 1 depicts a cross sectional view of a processing system 100. Thesystem 100 generally comprises a chamber body 102 coupled to a gassource 104. The chamber body 102 is typically a unitary, machinedstructure fabricated from a rigid block of material such as aluminum.Within the chamber body 102 is a showerhead 106 and a substrate supportassembly 108. The showerhead 106 is coupled to the upper surface or lidof the chamber body 102 and provides a uniform flow of gas from the gassource 104 that is dispersed over a substrate 101 positioned on asubstrate support assembly 108.

The substrate support assembly 108 generally comprises a substratesupport 110 and a stem 112. The stem 112 positions the substrate support110 within the chamber body 102. The substrate 101 is placed upon thesubstrate support 110 during processing. The substrate support 110 maybe a susceptor, a heater, an electrostatic chuck or a vacuum chuck.Typically, the substrate support 110 is fabricated from ceramic,aluminum, stainless steel or combinations thereof. The substrate support110 has a plurality of guide holes 118 disposed therethrough, each hole118 accommodating a lift pin 120 of a lift pin assembly 114.

The lift pin assembly 114 interacts with the substrate support 110 toposition the substrate 101 relative to the substrate support 110. Thelift pin assembly 114 typically includes the lift pins 120, a lift plate124 and an actuator 116. The elevation of the lift plate 124 iscontrolled by the actuator 116. The actuator 116 may be a pneumaticcylinder, hydraulic cylinder, lead screw, solenoid, stepper motor orother motion device that is typically positioned outside of theprocessing chamber 102 and adapted to move the lift plate 124. As thelift plate 124 is moved towards the substrate support 110, the liftplate 124 contacts the lower ends of the lift pins 120 to move the liftpins 120 through the substrate support 110. The upper ends of the liftpins 120 move away from the substrate support 110 and lift the substrate101 into a spaced-apart relation relative to the substrate support 110.

FIG. 2 is a sectional view of the lift pin assembly 114. The pluralityof lift pins 120 are disposed axially through the lift pin guide holes118 formed through the substrate support 110. The guide holes 118 may beintegrally formed in the substrate support 110, or may alternatively bedefined by an inner passage of a guide bushing 202 disposed in thesubstrate support 110 as depicted in FIG. 2. The guide bushing 202 istypically comprised of ceramic, stainless steel, aluminum or othersuitable material.

The lift pins 120 are typically comprised of ceramic, stainless steel,aluminum, or other suitable material. A cylindrical bearing surface 204of the lift pin 120 may additionally be treated to reduce friction andsurface wear. For example, the cylindrical bearing surface 204 of thelift pin 120 may be hard chromium plated or electropolished to reducefriction and make the bearing surface 204 harder, smoother, and moreresistant to scratching and corrosion.

A first end 206 of the lift pin 120 is flared to prevent the pin fromfalling through the guide hole 118 disposed through the substratesupport 110. The guide hole 118 is typically countersinked to allow thefirst end 206 to be positioned substantially flush with or slightlyrecessed from the substrate support 110 when the pin 120 is in a normalposition (i.e., retracted relative to the substrate support 110).

A second end 208 of the lift pin 120 extends beyond the underside of thesubstrate support 110 and is adapted be urged by the lift plate 124 toextend the first end 206 of the lift pin 120 above the substrate support110. The second end 208 may be rounded, flat or have another shape. Inone embodiment, the second end 208 is flat (i.e., oriented perpendicularto the center line of the lift pin 120). The flat second end 208 standsthe lift pin 120 on the lift plate 124, thereby maintaining the liftpins 120 substantially parallel to a central axis of the lift pins guideholes 118, advantageously reducing binding and contact between the pinand a lower edge 210 of the guide holes 118. Moreover, the self-standinglift pin 120 is easily centered within the lift pin guide hole 118,reducing the likelihood that the lift pin 120 will tilt or lean in theguide hole 118, thereby becoming jammed or scratched.

The lift pin 120 is designed to slide smoothly through the guide hole118 and features a shaft 230 having a larger diameter shoulder 232. Theshoulder 232 includes tapered ends 238A, 238B that transition theshoulder 232 and the other portions of the shaft 230. The shoulder 232bounds at least one relief region 236 formed between the shaft 230 andthe lift pin guide hole 118. As the lift pins 120 move through the guideholes 118, only two points (indicted by reference numerals 234) of thebearing surface 204 formed by the shoulder 232 are in contact with theguide hole 118, the probability of the lift pin 120 being scratched orjamming as a result of contact with the bottom edge 210 of the lift pinguide hole 118 is minimized.

FIGS. 3-6 depict sectional views of several alternate embodimentsaccording to the present invention. FIG. 3 depicts a lift pin 320 havinga flared end 326 and a large radius (rounded) end 328. The rounded end328 may have a full radius. A shaft 332 extends from the rounded end 328and is separated from a larger diameter shoulder 330 by a taperedtransition 334. The larger diameter shoulder 330 is the only part of thelift pin 320 that contacts the lift pin guide hole 118, while a reliefregion 336 is formed between the guide hole 118 of the guide bushing 202(shown in phantom) and the shaft 332. The length of the larger diametershoulder 330 is configured so that only the larger diameter shoulder 330contacts the guide hole 118 during movement of the lift pin 320.

FIG. 4 depicts a lift pin 420 that features a flared end 426, a largediameter section (shoulder) 430, a shaft 432, and a tapered transition434 that are similar to those of the lift pin 320. The lift pin 420additionally features a flat end 428 that promotes self-standing andcentering of the pin 420 within a guide hole (not shown).

FIG. 5 is an embodiment of a lift pin 520 having a larger diametershoulder 530 separating two narrower portions of a shaft 532. Theshoulder 530 transitions to the shaft 532 at two tapered ends 534A,534B. The shaft 532 is typically fabricated from aluminum, ceramic,stainless steel or other suitable material. The shaft 532 additionallyincludes a flared end 526 and a second end 528. The second end 528 istypically flat to promote self-standing of the lift pins 520 on liftplate 124 and centering of the lift pin 520 within the lift pin guidehole 118 (shown in phantom). Alternatively, the second end 528 of thelift pin 520 may be rounded.

The shoulder 530 is the only part of the lift pin 520 that contacts thelift pin guide hole 118, while defining relief regions 504A, 504Bbetween the guide hole 118 and shaft 532. The shoulder 530 is typicallyfabricated from a different material than the shaft 532. In oneembodiment, the shoulder 530 may be fabricated from stainless steelwhile the shaft 532 may be fabricated from another material, such asceramic or aluminum. The shoulder 530 may also be hard chromium platedor electropolished to improve the service life and performance of thelift pin 520. Alternatively, the shoulder 530 may be fabricated fromceramic or aluminum, and coupled to a shaft 532 fabricated from adifferent material.

FIG. 6 depicts another alternate embodiment of a lift pin 600 accordingto the present invention. A lift pin 600 comprises a shaft 632 and twooutwardly extending shoulders 630A, 630B spaced-apart along the lengthof the shaft 632. The lift pin 600 has a flared first end 626 and asecond end 628. The second end 628 may have large radius, be rounded orflat. The shaft 632 is typically fabricated from aluminum, ceramic,stainless steel or other suitable material.

The shoulders 630A, 630B contact a lift pin guide hole 118 (shown inphantom), while relief regions 602 are formed between the guide hole 118and the shaft 632 to minimize contact therebetween. The bearing surfaces622 of the shoulders 630A, 630B are typically rounded to provideessentially point contact of the lift pin 600 with the guide hole 118.The shoulders 630A, 630B may be fabricated from a single block ofmaterial with the shaft 632, or as independent elements coupledtogether, similar to the lift pin described above with reference to FIG.5. In one embodiment, the shoulders 630A, 630B are electropolishedstainless rings disposed on a ceramic shaft 632. The shoulders 630A,630B may alternatively be fabricated from ceramic or aluminum.

Therefore, an improved lift pin is provided that moves smoothly througha substrate support while minimizing particle generation typicallyassociated with the lift pin and substrate support contact. The lift pinof the present invention also reduces scratching, binding and galling ofthe lift pins, thereby improving the quality and useful life of the pinsso designed.

Although various embodiments which incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

1. An apparatus for selectively spacing a substrate from a substratesupport, comprising: a substrate support having a lift pin guide holedisposed through the substrate support; a lift pin shaft disposed withinthe lift pin guide hole, the lift pin shaft having at least a firstshoulder section circumscribing a portion of the lift pin shaft anddisposed movably within the lift pin guide hole; and a lift platedisposed proximate an end of the lift pin.
 2. The apparatus of claim 1further comprising: a lift pin guide disposed through a portion of thesubstrate support and having the lift pin guide hole formed therein. 3.The apparatus of claim 1, wherein at a gap is defined between the liftpin guide hole and the lift pin, the gap bounded on at least one side bythe first shoulder section.
 4. The apparatus of claim 1 furthercomprising: a second shoulder section disposed on the pin shaft in aspaced-apart relation to the first should section.
 5. The apparatus ofclaim 4, wherein the first shoulder section and the second shouldersection each comprise a rounded surface providing a bearing surfaceagainst the lift pin guide hole.
 6. The apparatus of claim 1, whereinthe pin shaft further comprises: a flat end; and a flared head disposedopposite the flat end.
 7. The apparatus of claim 1, wherein the firstshoulder section is comprised of a material different than the pinshaft.
 8. The apparatus of claim 1, wherein the first shoulder sectionis stainless steel and the pin shaft is ceramic.
 9. The apparatus ofclaim 1, wherein the first shoulder section is at least one of hardchromium plated or electropolished.
 10. The apparatus of claim 1,wherein the pin shaft comprises one or more sections of lesser diameterthan the first shoulder section.
 11. The apparatus of claim 1, whereinthe first shoulder section includes tapered ends that transition thefirst shoulder section and the pin shaft.
 12. An apparatus forselectively spacing a substrate from a substrate support, comprising: apin shaft having a first diameter section and a second diameter section;a flared end adapted to support the substrate thereon and coupled to thefirst diameter section of the pin shaft; a first shoulder sectionconnected concentrically to the pin shaft between the first diametersection and the second diameter section, the first shoulder sectionhaving a diameter greater than the first diameter section and the seconddiameter section of the pin shaft; and a substrate support having a holeformed therethrough, the hole having the first shoulder section of thepin shaft movably disposed therein.
 13. The apparatus of claim 12,wherein an end of the first shoulder section disposed away from theflared end is at a distance from the flared end that is less than alength of the hole through the substrate support in which the pin shaftis disposed.
 14. The apparatus of claim 12, wherein the pin shaftfurther comprises a flat end opposite the flared head.
 15. The apparatusof claim 12, wherein the first shoulder section is comprised of amaterial different than the pin shaft.
 16. The apparatus of claim 15,wherein the shoulder section is stainless steel and the pin shaft isceramic.
 17. The apparatus of claim 12 further comprising: a secondshoulder section disposed on the pin shaft in a spaced-apart relation tothe first should section.
 18. A method for spacing a substrate from asubstrate support, comprising: elevating a lift plate to urge aplurality of lift pins in an upwards direction; and moving the lift pinsthrough a substrate support while maintaining at least a first contactpoint of each of the lift pins in contact with the substrate supportwhile the lift pins move.
 19. The method of claim 18, wherein the stepof moving further comprises: maintaining a second contact point of eachof the lift pins in contact with the substrate support while the liftpins move.
 20. The method of claim 18, wherein the step of elevating thelift plate to further comprises: contacting the lift plate to a flat endof each of the lift pins to orientate each lift pin perpendicular to aplane of the lift plate.